Breast cancer will attack 150,000 US women in 1992, and HER2 is amplified and overexpressed in about 30% of both advanced and early stage mammary tumors. Pancreatic cancer will attack 30,000 US men and women in 1992 and is fatal in virtually all patients. Over 80% of pancreatic tumors display c-Ki-ras oncogenes with 12th codon mutations. Antisense and antigene DNA therapeutics offer powerful tools for intervention against activated oncogenes in malignant cells. The goal of this proposal is to specifically ablate HER-2 overexpression in breast cancer, and mutant c-Ki-ras expression in pancreatic cancer. Three different novel DNA derivatives will be utilized, in four different delivery modes, to find a combination which will yield maximum efficacy. The DNA derivatives will be tested for efficacy against fresh human tumor xenografts in immunocompromised mice. Successful derivatives will be ready for formulation studies and small/large animal toxicology testing by the conclusion of this funding period. In this project, fresh human tumor samples will first be implanted in immunocompromised mice. These xenografts will then be screened for HER- 2 gene amplification and protein overexpression in the case of breast tissue. Pancreatic cancer xenografts will be screened for the presence of codon 12 c-Ki-ras mutants. To inhibit HER-2 protein expression, antisense DNAs will be prepared against the 5' end of the mRNA(5'-dCCA ATG GAG GGG AAT), and antigene DNAs against an oligopurine-oligopyrimidine region in the promoter (5'-dGGTGGTGGTTGTGGT). To inhibit c-Ki-ras protein expression, antisense DNAs will be prepared against the two most frequently observed mutant sequences (5'dTAC GCC AAC AGC TCC and 5'dTAC GCC ATC AGC TCC). For each sequence, DNA borane phosphonates, DNA phosphorodithioates, and stereospecific DNA methylphosphonates will be synthesized, as well as sense and scrambled controls. The DNA derivatives will be administered intraperitoneally, orally, and by micropump in solution, and intravenously in liposomes.